Immunohistochemical detection of the sodium-calcium exchanger in rat hippocampus cultures using subtype-specific antibodies.

All of the known Na+/Ca2+ exchanger subtypes, NCX1-3, are expressed in the brain, albeit with marked regional differences. On the mRNA level, overall expression seems most prominent for NCX2, intermediate for NCX1, and, except for a few regions, low for NCX3. Using three subtype-specific antibodies, we have now studied the cellular expression of the NCX subtypes in rat hippocampus cultures by immunohistochemical techniques. Our results provide evidence for a highly cell-specific expression pattern of NCX subtypes and show surprisingly little colocalization. NCX1 and NCX3 are both primarily expressed in neuronal cells. While NCX1 is found in the large majority of neurons, NCX3 expression was restricted to a small minority of cells. By contrast, NCX2 was almost exclusively present in glial cells. The NCX2 antibody, a IgM, stained glial cell membranes as well as an intermediate fibrillar system. In spite of extensive screening, the nature of this fiber system has not yet been identified.